The invention concerns a fifth wheel for a truck, with a coupling plate and with means to fasten the fifth wheel to the vehicle frame in the form of two pivot pins, which are fashioned at the side at two diametrically opposite places underneath the top of the coupling plate on the fifth wheel and which project out to the side beyond the coupling plate, and which have a bearing segment and a fastening segment.
Fifth wheels are mounted in bearing pedestals, which are either an integral part of the vehicle frame or are screwed onto the vehicle frame and can swivel about a horizontal axis. The bearing pedestal is connected to the fifth wheel by bolts, which are inserted into the bearing pedestal and corresponding openings of the coupling plate. Bearing pedestals which are fastened on the vehicle frame or which are integral parts of the vehicle frame are known, for example, from EP 00 87 903 B1 and DE 43 22 717 A1. These bearing pedestals have a bearing tube, through which the bearing bolts can be inserted.
Moreover, there are fifth wheels that have pockets with inserted rubber bearings underneath the coupling plate. Here as well the fastening to the bearing pedestals is done by bearing pins, which are inserted into the side walls of the pockets and through the bearing pedestal. Such arrangements are known from DE-PS 23 03 163, DE 30 40 925 C2, EP 0 038 928, EP 0 114 046 and DE-PS 14 30 462.
All solutions have the common drawback that the fifth wheel during assembly must be oriented exactly to the frame and, thus, to the openings of the bearing pedestals before the bearing bolts can be inserted. This requires considerable assembly expense. A further disadvantage results from the manufacturing tolerances of the vehicle frame. The frame pieces and, thus, the spacing of the bearing pedestals can be of different size, so that a stable fastening of the fifth wheel cannot always be achieved without resorting to additional steps.
The drawbacks of these known designs with inserted bearing bolts or bearing pins are avoided by the above-mentioned fifth wheel with the pivot pins arranged on both sides directly on the fifth wheel, having a bearing segment and a fastening segment. The bearing segment is that part of the pivot pin which lies in the bearing pedestal. The fastening segment, instead, is responsible for mounting on the fifth wheel.
This design has become known, for example, through DE 28 36 703 A 1 and U.S. Pat. No. 3,198,548.
Through this known design, the assembly is significantly facilitated and, thus, the assembly time is shortened. The fifth wheel is lowered from above onto the vehicle frame, the pivot pins engaging with recesses of the bearing pedestal, arranged on the vehicle frame. The fifth wheel adjusts itself, without requiring additional measures. After this, the pivot pins are secured to the bearing pedestal by means of a corresponding fastening means, which shall be discussed hereafter in connection with the bearing pedestal.
Furthermore, manufacturing tolerances of the vehicle frame can be equalized. The pivot pins can be made to excess length, so that even when the frame spacing is too large a secure fastening on the bearing pedestal of the vehicle frame can be assured. If, at normal frame spacing, the pivot pins then project slightly to the outside from the bearing pedestal, this is acceptable.
In such a mounting of the fifth wheel, the fastening of the two pivot pins to the coupling plate becomes especially important, since they must convey the forces emanating from the fifth wheel plate during operation and diverted into the vehicle frame.
In the known fifth wheels, therefore, the pivot pins are joined to the fifth wheel as a single piece (material closure), in particular, welded, as specifically stated in the U.S. patent.
This type of fastening has the major disadvantage that, for applications which require different bearing bolts for the same fifth wheel plate, entire fifth wheel plates must be kept on hand with the corresponding bearing bolts each time. This circumstance increases the logistical expense, in particular, inventory is more costly, and it also prevents a modular system.